1. Field of the Invention
The present invention relates in general to a method for treating phytophotodermatitis and, more particularly, to a method for treating phytophotodermatitis caused by exposure to linear and/or non-linear (e.g., angular) furanocoumarins and derivatives thereof—among other chemical compounds.
2. Background Art
Phytophotodermatitis (hereinafter sometimes referred to “PPD”) is traditionally expressed as a cutaneous phototoxic inflammatory response and/or eruption resulting from exposure to one or more photosensitizing, chemical compounds (e.g., botanical substances) and electromagnetic radiation (e.g., ultraviolet (UV) radiation) emanating primarily from the sun.
The photosensitizing, chemical compounds or skin toxins that result in human phytophotodermatitis are traditionally produced by members of several plant families including, but not limited to, Umbelliferae, Leguminosae, Apiaceae, Rutaceae, Moraceae, Roasceae, Asteraceae, Brassicaceae, Clusiaceae, Convolvulaceae, Anacardiaceae, Fabaceae, and Ranunculaceae. Common plants implicated in these families include, but are not limited to, celery, giant hogweed, angelica, parsnip, fennel, dill, anise, parsley, lime, lemon, rue, fig, mustard, scurf pea, and chrysanthemums—just to name a few. Notably, giant hogweed is so problematic that the United States Government regulates it as a federal noxious weed.
Among the skin toxins produced by plants in the above-identified plant families are furanocoumarins including, but not limited to, psoralen, 8-isopentenyloxypsoralen (imperatorin), 5-hydroxypsoralen (bergaptol), 5-methoxypsoralen (5-MOP), 8-hydroxypsoralen (xanthotoxol), 8-methoxypsoralen (8-MOP), 5,8-dihydroxypsoralen, 5,8-dimethoxypsoralen (isopimpinellin), angelicin, and sphondin. Chemical structures of non-limiting, representative furanocoumarins are provided below.

It is believed that exposure to electromagnetic radiation, such as UV-A light enables furanocoumarins to absorb energy, thereby altering reactivity of their molecular structures, as well as attain activated, high-energy states. In the presence of oxygen, activated molecules are believed to form photoaddition products with DNA pyrimidine bases via DNA interstrand crosslinking at cytosine and thymidine with the furan ring of the furanocoumarins, which results in epidermal cell nucleic damage. In the absence of oxygen, activated furanocoumarins are also believed to produce oxygen, superoxides, and hydroxy radicals, which are believed cause cellular membrane damage.
Responses and/or eruptions from PPD typically begin approximately 24 hours after exposure and peak between approximately 48 hours and approximately 72 hours after exposure. □Phytophotodermatitis normally manifests as a burning erythema that is often followed by blistering, epidermal necrosis, and/or desquamation. Postinflammatory hyperpigmentation lasting weeks to several months typically follows the acute response and/or eruption from PPD. Affected areas often remain hypersensitive to UV radiation for many years and re-eruptions of lesions and blisters is common.
Until now, the only known antidote for contact with and/or exposure to these skin toxins was to immediately wash the skin thoroughly with soap and water, thereby removing at least some of the toxins and hopefully minimizing any reaction with subsequent exposure to sunlight. Unfortunately, the average victim is usually not aware of exposure to the photosensitizing, chemical compounds until a response and/or eruption occurs and problematic symptoms begin to manifest. Once this has occurred, washing with soap and water is ineffective and potentially contraindicated for certain reactions—likely because the plant toxins have penetrated into the epidermis and/or dermis. Currently, it is recommended that once problematic symptoms begin to manifest, professional medical advice should be sought immediately because medical treatment with prescription topical steroids may reduce the severity of a person's reaction. It is further currently recommended to cover any burns and blisters with sterile dressings to prevent infection, and to wear clothing that shields the skin from sunlight. Long-term, use of sun block in subsequent years and the wearing of sun protective clothing may be required to prevent sensitization by sunlight.
While the above-identified medical treatments do appear to provide at least some relief to those who are afflicted by phytophotodermatitis, such treatment remains non-desirous and/or problematic inasmuch as, among other things, none of the above-identified treatments provide sufficient therapeutic relief from the debilitating effects of PPD.
It is therefore an object of the present invention to provide a method for treating phytophotodermatitis which offers timely relief from the symptoms presented when one is afflicted with PPD.
These and other objects of the present invention will become apparent in